As-Produced Intrinsic Physico-Chemical Properties and Appropriate Characterization Tools - Safety of Nanomaterials along Their Lifecycle - page 2

surface-to-volume ratio results in an increase in the particle surface energy, which
may render them more reactive.
One of the major challenges in determining risks emerging from nanomaterials is
their extremely wide diversity, in terms of not only different sizes but also a variety
of shapes and compositions, or different surface chemistry and surface charge. An
additional issue is the possible presence of impurities. When conducting any biologi-
cal evaluation of a nanomaterial, it is important to know with completeness what
substance is being tested. The main physico-chemical properties of nanomaterials
can be organized into three general groups that can answer fundamental questions
concerning nanomaterial characterization:

• What does the material look like?

• Size/size distribution

• Agglomeration/aggregation state

• Shape

• Specific surface area

• What is the material made of?

• Composition (including chemical composition, crystal structure, and

impurities)

• Surface chemistry

• What factors affect the material interaction with its surroundings?

• Surface charge

• Solubility

• Dispersibility

Different methods are available for the characterization of the nanomaterial
properties. They are listed in Table 1.1 with relevant characterization standards.
However, the majority of those methods have not necessarily been validated for
different types of nano-objects. Thus, there is an urgent need for the development
of additional measuring techniques. The standardization of the new methods is
currently being undertaken by the International Organization for Standardization
(ISO) technical committees (ISO/TC 20, ISO/TC 24, and ISO/TC 229). A vari-
ety of tools and methods for nanomaterial characterization are also being recom-
mended by some international, as well as host nation organizations such as the
Organization for Economic Co-operation and Development (OECD), the American
Society for Testing and Materials (ASTM International), the U.S. Environmental
Protection Agency (EPA), or the U.S. National Cancer Institute-Nanotechnology
Characterization Laboratory.
Relevant methods are listed in the Registration, Evaluation, Authorisation and
Restriction of Chemicals guidance for nanospecific characterization (ECHA 2012),
in accord with the OECD sponsorship program (OECD 2010), and the methods were
selected here by their proven reliability for nanomaterial characterization in indus-
trial research and development.